1. Field of the Invention
The present invention relates to a copier, printer, facsimile apparatus or similar electrophotographic image forming apparatus and more particularly to a toner container to be removably mounted to an image forming apparatus for replenishing toner to a developing device.
2. Description of the Background Art
While a toner container mounted to an image forming apparatus is usually replaced by the user, the replacement often causes toner to scatter and is awkward to perform. A toner container easy to mount and dismount without causing toner to scatter has been proposed in various forms in the past. For example, a toner container whose cap is automatically opened when the container is moved and is therefore easy to use is available. However, this kind of toner container has sophisticated, expensive structure.
There has been proposed an image forming apparatus and a toner container constructed to solve the above problem. The toner container has its toner outlet automatically opened when simply inserted into the setting portion of the apparatus from the above or has it automatically closed when simply pulled out of the setting portion. A nozzle extends upward from the setting portion. The toner container includes a self-closing valve that opens when the nozzle is inserted into the toner container. The self-closing valve is implemented as a sponge seal formed of compressed foam sponge non-permeable to air and formed with a cruciform slit. The sponge seal elastically deforms when the nozzle is inserted into the slit of the seal or closes the slit when the nozzle is removed from the slit, thereby preventing toner from leaking.
However, the problem with the sponge seal is that the elastic restoring force is apt to decrease due to, e.g., creep when the seal hardens in a low-temperature environment or due to aging. The sponge seal reduced in restoring force often causes the toner to leak when the toner is pulled out of the setting portion. Particularly, the toner outlet is positioned at the bottom of the toner container. Therefore, when the closing movement of the sponge seal is delayed at the time of mounting or dismounting of the toner container, the toner scatters around the setting portion due to its own weight. Moreover, the nozzle is apt to tear off or shave off the sponge seal at the time of mounting and dismounting. The resulting pieces of the sponge seal would degrade image quality if introduced in the developing device.
It has been proposed to dispose a mechanical shutter, which closes under the action of a spring, in the toner container. The mechanical shutter, however, reduces the substantial area of the portion of the toner container that leads to the toner outlet, causing the toner to bridge. Particularly, it is likely that, a flexible toner bag forming part of the toner container is folded or inclined, aggravating the bridging of the toner.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 7-20702, 9-197818 and 2000-267415.